This invention relates to marine propellers, and more particularly, to a foldable marine propeller assembly.
Foldable marine propellers which employ a pair of pivotally mounted blades that move between a trailing, collapsed position and an outflung drive position are known. Such foldable marine propellers are commonly connected to a drive shaft by a shear pin to avoid damage to the drive shaft should excessive torque forces be developed. Representative prior art constructions of foldable propellers are disclosed in the following United States patents:
______________________________________ Learnard 725,097 April 14, 1903 Godfrey 2,608,257 August 26, 1952 Beck 3,255,826 June 14, 1966 Butler 3,591,311 July 6, 1971 Lorenz 3,709,634 January 9, 1973 Kettner 3,715,171 February 6, 1973 Ehrenskjold et al 3,981,613 September 21, 1976 Beck 3,982,853 September 28, 1976 ______________________________________
The abrupt opening of the foldable propeller blades to the operative position can in itself create reactive torque forces that are sufficiently large to fracture the shear pin. None of the above patents discloses a means for absorbing this reactive force to lessen the chance of fracturing the shear pin under these circumstances.